The effectiveness of selection based on the selection index highly productive daughters of bulls with breeding categories, installed using a modified method

Abstract

The selection of sires based on the quality of their offspring still remains relevant for increasing the milk productivity of cattle, as well as the selection of highly productive cows based on a selection index that takes into account the exterior characteristics of animals. The purpose of the study was to test the method modified by the authors for determining the categories of breeding value of sires of dairy and dairy-meat breeds and to establish the effectiveness of selection based on the selection index of highly productive daughters of sires with different breeding values. The studies were conducted in 2025–2026. in LLC «Malka» Zolsky district of the Kabardino-Balkarian Republic on first-calf cows of the red steppe breed, daughters of three sires – Valet 117 (28 daughters), Napor 905 (28 daughters), Parus 21 (25 daughters). In the course of the study, it was established that among the offspring of sires compared by quality, the sire Parus 21 (A3) showed an improving effect in terms of milk yield, and the sire Napor 905 (B2) showed an improving effect in milk fat content. In terms of milk protein content, the Napor 905 sire turned out to be an improver of the second category (B2), and the remaining sires were neutral (N). The daughters of sire bulls with the highest value of the selection index were superior to their half-sisters with the lowest value of the selection index in terms of milk yield per lactation by 9.8–18.9% (p>0.95–0.99), in fat milk content – by 0.16–0.33 abs.% (p>0.95–0.999), in milk protein content – by 0.02–0.04 abs.% (p<0.95). Of the two factors studied, the greatest influence on milk yield and fat content was exerted by the selection index (48.4 and 16.0% (p>0.999)), the least – by the sire (2.1 and 4.3% (p<0.95)).